Epics don't come bigger than The Avengers, a spectacle of corporate synergy supported by a massive budget, an army of marketing partners and 50 years of comic-book source material from which to draw. After a half-decade of prep work in their own solo movies, Marvel's mightiest superheroes have been assembled under one roof to save the world, and the result is a rousing, crowd-pleasing and smart action adventure that is as much a showpiece of modern blockbuster-making as it is of time-tested narrative tropes.

It's also the movie that makes it safe for us to love 9/11 again, offering visions of Manhattan skyscrapers leveled by merciless alien hordes and scenes of first responders charging bravely into the mayhem, but somehow, blown up to silver screen size, the sight of crumbling debris tumbling from the sky and smashing dirty-water hot dog carts is strangely comforting. Just as Star Wars made combat seem thrilling once more for jaded post-Vietnam crowds, The Avengers makes it easy for an audience to revel in the sheer, guilt-free joy of mass destruction. In some ways, it feels like the kick-off to the afterparty for a post-Iraq War nation, with a sense of "mission accomplished" back-slapping buried beneath all the pyrotechnics. Iron Man and Captain America in particular are avatars of American "exceptionalism," as Fox News might call it, totems of faith in science, industrial might and the innate righteousness of hard work to win the day. There is even a shadowy, extra national U.N.-like Security Council that has its own sometimes-sinister agenda, just to rile up the outrage of far-right conspiracy buffs. Yet even as it celebrates good old-fashioned American jingoism, The Avengers stresses the importance of strong-willed individuals joining in a collective effort for the greater societal good, which smacks of bipartisan consensus-making at its finest.

Of course, the political subtext never gets in the way of a good time, as super-geek Joss Whedon brings the same zippy mix of quick, sarcastic patter and myth-obsessive fussiness that made his Buffy the Vampire Slayer and Firefly series so beloved.

Whedon smartly keeps the focus on characterization, giving the heroes personality where they easily could've just been action figures moving around a game board. Joss takes his clues from the originals created by Stan Lee and Jack Kirby, gently modernizing the realistic neurotic tics and squabbling that made Marvel's funny books so inventive in the Mad Men era.

Robert Downey Jr.'s Iron Man and Tony Stark is like a hybrid of Mark Cuban and Steve Jobs with lasers strapped to his back, a nonstop party machine with profoundly altruistic impulses beneath his flash and constantly flapping motormouth. Chris Hemsworth's pitch-perfect Thor is a gallant goofball, a noble warrior possessed of the hearty, natural self-confidence you might imagine in a dude that controls thunderclouds. Others have a bit more battle damage: The aw-shucks, New Deal optimism of Chris Evans' Captain America is married to skepticism about this brave new world he's woken up in, and first-hand awareness — from World War II — of the evil that men do. Sam Jackson's Nick Fury and Scarlett Johansson's Black Widow have the grit and knowing cynicism of professional super spies, though a bit more of Jackson's trademark flair would've been nice. Jeremy Renner's expert sniper Hawkeye is somewhat bland, deprived of his traditional comic book smartass role, which has been usurped by Stark, who gets the bulk of the wisecracks. Mark Ruffalo is good, though a hint too glib as Dr. Bruce Banner, the Hulk's superego, lacking the intensity that Edward Norton brought to the part. Tom Hiddleston is a sly treat as the trickster Loki, who recruits a scary otherworldly army to help him finally suppress these pesky humans who stubbornly refuse to submit to being ruled.

Everything here is meant to shock, awe and amuse, and it does, with oversized laugh-out-loud gags, breathtaking action, and ample catnip for the geek faithful. The effects work is predictably stellar, especially on the CGI Hulk, who at last looks like a magnificent monster, and not a big green claymation mess with balloon muscles. The only real problem is an excessively long running time that makes the plot needlessly complicated, and 3-D that adds next to nothing, other than heft to the ticket price and thin coat of darkness to the image. Then again, what is an all-American product without a little pointless upsizing?